# How do I know if I need replica shards?
**URL:** https://discuss.elastic.co/t/how-do-i-know-if-i-need-replica-shards/19403
**Category:** Elasticsearch
**Created:** [August 22, 2014, 7:16am UTC](https://discuss.elastic.co/t/how-do-i-know-if-i-need-replica-shards/19403 "2014-08-22T07:16:15Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@ElasticSearch\_Users\_](https://discuss.elastic.co/u/ElasticSearch_Users_)
#### Post date: [August 22, 2014, 7:16am UTC](https://discuss.elastic.co/t/how-do-i-know-if-i-need-replica-shards/19403/1 "2014-08-22T07:16:15Z")
Hi,
If I have setup a 3 node cluster, deployed one index with 20 shards.
How can I determine that my current setup is inadequate, and I need to add
one replica or two replica shards per primary shards?
Even if I add another data node, I may get 5 primary shards on each, now if
that distributes load evenly, what is the need for replica shards?
IMPORTANT: Please note that my query will not be specific to a group of
shards, I mean, there is no way, I can route or classify my query as only
hitting a subsection of shards. It will actually go to all shards for every
search query.
Appreciate your response.
Thanks,
Sandeep
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### Author:  [@ElasticSearch\_Users\_](https://discuss.elastic.co/u/ElasticSearch_Users_)
#### Post date: [August 22, 2014, 7:27am UTC](https://discuss.elastic.co/t/how-do-i-know-if-i-need-replica-shards/19403/2 "2014-08-22T07:27:06Z")
Just want to add that my intention is not high availability or failover. It
is more w.r.t. how performance will improve in such a scenario?
I believe, only if you have more nodes or you current nodes are
underutilized, would you think of this. But how do you determine that?
Thanks
Sandeep
On Friday, 22 August 2014 12:46:16 UTC+5:30, Sandeep Ramesh Khanzode wrote:
> Hi,
>
> If I have setup a 3 node cluster, deployed one index with 20 shards.
>
> How can I determine that my current setup is inadequate, and I need to add
> one replica or two replica shards per primary shards?
>
> Even if I add another data node, I may get 5 primary shards on each, now
> if that distributes load evenly, what is the need for replica shards?
>
> IMPORTANT: Please note that my query will not be specific to a group of
> shards, I mean, there is no way, I can route or classify my query as only
> hitting a subsection of shards. It will actually go to all shards for every
> search query.
>
> Appreciate your response.
>
> Thanks,
> Sandeep
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [July 6, 2017, 1:07am UTC](https://discuss.elastic.co/t/how-do-i-know-if-i-need-replica-shards/19403/3 "2017-07-06T01:07:03Z")